¹Flow Cytometry Unit, Haematology Department, Leukaemia Research Laboratory, Westmead Hospital, University of Sydney, Sydney, Australia

Correspondence: Dr MM Sartor, Flow Cytometry Unit, Haematology Department, Leukaemia Research Laboratory, Westmead Hospital, University of Sydney, Darcy Road, Westmead, Sydney, NSW 2145, Australia. E-mail: mary@icpmr.wsahs.nsw.gov.au

Received 14 March 2007; Revised 23 May 2007; Accepted 4 July 2007; Published online 20 August 2007.

Abstract

In this study, we retrospectively analysed the utility of CD110 expression on CD34⁺ cells as a predictor of delayed platelet transfusion independence in 39 patients who underwent autologous peripheral blood stem cell transplantation. Absolute CD34⁺ cells and CD34⁺ subsets expressing CD110 were enumerated using flow cytometry. Of the 39 patients, 7 required 21 days or more to achieve platelet transfusion independence. Six of the seven patients received a dose of CD34⁺CD110⁺ cells below 6.0 10⁴/kg while 30 of 32 patients who achieved platelet transfusion independence in <21 days received a dose of CD34⁺CD110⁺ cells >6.0 10⁴/kg (P<0.001). Patients with delayed platelet engraftment received a median dose of 5.2 10⁴ CD34⁺CD110⁺ cells/kg compared with a median dose of 16.4 10⁴ cells/kg for those engrafting within 21 days (P=0.003). Further analysis showed that >6.0 10⁴ CD34⁺CD110⁺ cells/kg was highly sensitive (93.8%) and highly specific (85.7%) for achieving platelet transfusion independence within 21 days. Delay in platelet transfusion independence translated into an increased requirement for platelet transfusion (median 6 vs 2 transfusions, P<0.0001). The dose of CD34⁺/CD110⁺ cells/kg infused at time of transplantation appears to be an important factor identifying patients at risk of delayed platelet engraftment.